1. Field of the Invention
The present general inventive concept relates to an image device capable of reverse play, and a method thereof. More particularly, the present general inventive concept relates to an image device capable of rapid reverse play without cutoff, and a method thereof.
2. Description of the Related Art
Image devices play or record broadcasting, images recorded on recording media, images transmitted from an external device, etc. They have trick play modes including fast forward play, normal forward play, slow forward play, fast reverse play, and reverse play modes.
Image devices which play images compressed in a Motion Picture Experts Group (MPEG) format have many problems when performing reverse play. This results from the types of picture provided in the MPEG format.
The types of picture provided in the MPEG format can be divided into an Intra-coded (I) picture, a Predicted-coded (P) picture and a Bidirectionally predicted-coded (B) picture. The I picture performs discrete cosine transform and decoding of a picture without using motion compensation. The P picture performs motion compensation based on an I picture or another P picture, and then performs discrete cosine transform of the remaining differential. The B picture performs motion compensation similarly to the P picture, but performs motion compensation from two frames positioned at the front and back of a time axis unlike the P picture.
Additionally, a picture transmission sequence in MPEG format has structures like I, P, P, P, P. On the basis of the transmission sequence, a group of pictures (GOP) indicates the pictures from an initial I picture until the next I picture. If the number of pictures in the GOP is set as M, the number of pictures of each GOP in one video sequence varies.
Accordingly, as a GOP can be formed in many ways according to the type and the number of pictures, image devices have difficulty in performing reverse play.
Recently, there has been the problem that only I pictures are reverse-played but other pictures are cut off when performing reverse play. In addition, P pictures as well as I pictures are reverse-played by storing one GOP in a buffer. However, when one GOP is stored in the buffer and reverse-played, if reverse play of the GOP is finished, a previous GOP is decoded, stored in the buffer and then reverse-played, resulting in a time delay.